This build is from the Threshold 2 development branch and each of these builds take us closer to the release of the first significant update to Windows 10 since its release back on 29 July 2015.

I have this installed on my test HP Spectre x360 and it has been very stable since I installed it earlier this week.

If you are running the last Slow Ring build of Windows 10, which was 10240 - the release build, then this will be a significant update for you as there have been four interim builds sent out to Fast Ring testers since late July.